Led temperature-dependent power supply system and method

ABSTRACT

A LED based lighting system ( 20 ) employs a LED load temperature sensor ( 40 ) for generating a temperature-sensing signal (TSS) indicative of an operational temperature of the LED load ( 10 ), a LED current sensor ( 50 ) for generating a current-sensing signal (CSS) indicative of a flow of the LED current (I LED ) through the LED load ( 10 ), and a LED driver ( 30 ) for regulating the flow of the LED current (I LED ) through the LED load ( 10 ) as a function a mixture of the current-sensing signal (CSS) and the temperature-sensing signal (TSS). The system ( 20 ) can further employ a driver disable notifier ( 80 ) and a LED driver disabler ( 90 ), or alternatively, a fuse network ( 100 ) for disabling the LED driver ( 30 ) upon a detection of a fault condition of the system ( 20 ).

The present invention generally relates to light-emitting diode (“LED”)light sources. The present invention specifically relates to a powersupply system for LED light sources employed within lighting devices(e.g., a traffic light).

Most conventional traffic lighting systems employ incandescent bulbs aslight sources. Typically, a power disable notifying system is utilizedto detect bulb malfunction. Unfortunately, energy consumption andmaintenance of incandescent bulb systems is unacceptably high. As aresult, LEDs are rapidly replacing incandescent bulbs as the lightsource for traffic signals. Typically, LEDs consume ten percent (10%) ofthe power consumed by incandescent bulbs when providing the same lightoutput (e.g., 15 watts vs. 150 watts). Additionally, LEDs experience alonger useful life as compared to incandescent bulbs resulting in areduction in maintenance.

The use of LEDs as the light source for traffic signals has resulted indevelopment of LED power supplies, which convert an alternating current(AC) voltage input (e.g., 120 VAC) to a direct current (DC) voltageinput. The present invention advances the art of supplying power to LEDtraffic lighting systems.

One form of the present invention is a LED temperature-dependent powersupply system comprising a LED driver module, and atemperature-dependent current control module. The LED driver moduleregulates a flow of a LED current through a LED load as a function of atemperature-dependent feedback signal. The temperature-dependent currentcontrol module generates the temperature-dependent feedback signal as afunction of the flow of LED current through the LED load and anoperating temperature of the LED load. The temperature-dependent currentcontrol module is in electrical communication with the power supply tocommunicate the temperature-dependent feedback signal to the LED drivermodule.

The term “electrical communication” is defined herein as an electricalconnection, electrical coupling or any other technique for electricallyapplying an output of one device (e.g., the temperature-dependentcurrent control module) to an input of another device (e.g., the LEDdriver module).

A second form of the present invention is a LED temperature-dependentpower supply method involving a generation of a current-sensing signalindicative of a flow of a LED current through a LED load, a generationof a temperature-sensing signal indicative of an operating temperatureof the LED load, and a regulation of the flow of the LED current throughthe LED load as a function of a mixture of the current-sensing signaland the temperature-sensing signal.

The term “mixture” is defined herein as a generation of an output signal(e.g., the temperature-dependent feedback signal) having a mathematicalrelationship with each input signal (e.g., the current-sensing signaland the temperature-sensing signal).

The foregoing forms as well as other forms, features and advantages ofthe present invention will become further apparent from the followingdetailed description of the presently preferred embodiments, read inconjunction with the accompanying drawings. The detailed description anddrawings are merely illustrative of the present invention rather thanlimiting, the scope of the present invention being defined by theappended claims and equivalents thereof.

FIG. 1 illustrates a block diagram of a LED temperature-dependent powersupply system in accordance with a first embodiment of the presentinvention;

FIG. 2 illustrates one embodiment in accordance with the presentinvention of the LED temperature-dependent power supply systemillustrated in FIG. 1;

FIG. 3 illustrates an exemplary graphical relationship of a LED currentand a negative temperature coefficient network illustrated in FIG. 2;

FIG. 4 illustrates a table listing various operational states oftransistors employed by the temperature-dependent power supply systemillustrated in FIG. 2;

FIG. 5 illustrates a block diagram of a LED temperature-dependent powersupply system in accordance with a second embodiment of the presentinvention;

FIG. 6 illustrates one embodiment in accordance with the presentinvention of the LED temperature-dependent power supply systemillustrated in FIG. 5; and

FIG. 7 illustrates a table listing various operational states oftransistors employed by the temperature-dependent power supply systemillustrated in FIG. 5.

A LED based lighting system 20 (e.g., a traffic light) as illustrated inFIG. 1 controls a flow of a LED current I_(LED) through a LED load(“LL”) 10 of one or more LEDs in response to an input voltage in theform of either an “ON” state input voltage V_(ON) or an “OFF” stageinput voltage V_(OFF). To this end, system 20 employs a LED driver(“LD”) 30, a LED load temperature sensor (“LLTS”) 40, a LED currentsensor (“LCS”) 50, a temperature-dependent current controller (“TDCC”)60, a fault detector (“FD”) 70, a driver disable notifier (“DDN”) 80 anda LED driver disabler (“LDD”) 90.

LED driver 30 is an electronic module structurally configured to apply aLED voltage V_(LED) to LED load 10 and to regulate a flow of LED currentI_(LED) through LED load 10 as a function of operating temperature ofLED load 10 and the flow of LED current I_(LED) through LED load 10 asindicated by a temperature-dependent feedback signal TDFS communicatedto LED driver 30 by control controller 60. The amperage level of LEDcurrent I_(LED) exceeds a minimum forward current threshold for drivingLED load 10 in emitting a light whenever the “ON” state input voltageV_(ON) is applied to LED driver 30. The amperage level of LED currentI_(LED) is less than the minimum forward current threshold for drivingLED load 10 in emitting a light whenever the “OFF” state input voltageV_(OFF) is applied to LED driver 30.

The manner in which LED driver 30 regulates the flow of LED currentI_(LED) through the LED load 10 is without limit. In one embodiment, LEDdriver 30 implements a pulse-width modulation technique in regulatingthe flow of the LED current I_(LED) through LED load 10 where theimplementation of the pulse-width modulation technique is based ontemperature-dependent feedback signal TDFS.

LED driver 30 is also structurally configured in the to generate a shortcondition fault signal SCFS whenever LED load 10 is operating as a shortcircuit. LED driver 30 is in electrical communication with faultdetector 70 to communicate short condition fault signal SCFS to faultdetector 70 upon a generation of short condition fault signal SCFS byLED driver 30. In one embodiment, an operation of LED load 10 operatingas a short circuit encompasses a low LED voltage condition whereby thevoltage level of LED voltage V_(LED) is insufficient for driving LEDload 10 in emitting a light during an application of the “ON” stateinput voltage V_(ON) to LED driver 30.

The manner in which LED driver 30 generates the short condition faultsignal SCFS is without limit. In one embodiment, LED voltage V_(LED) iscommunicated to fault detector 70 whereby LED voltage V_(LED) beingbelow a short condition fault threshold constitutes a generation of theshort condition fault signal SCFS.

Sensor 40 is an electronic module structurally configured to sense anoperating temperature of LED load 10, and to generate atemperature-sensing signal TSS that is indicative of the operatingtemperature of LED load 10 as sensed by sensor 40. Sensor 40 is inthermal communication with LED load 10 to thereby sense the operatingtemperature of LED load 10, and is in electrical communication withcurrent controller 60 to communicate temperature-sensing signal TSS tocurrent controller 60. The term “thermal communication” is definedherein as a thermal coupling, a spatial disposition, or any othertechnique for facilitating a transfer of thermal energy from one device(e.g., LED load 10) to another device (e.g., sensor 40).

The manner in which sensor 40 senses the operating temperature of LEDload 10 and generates temperature-sensing signal is without limit. Inone embodiment, sensor 40 employs an impedance network having atemperature-coefficient resistor, positive or negative, fabricated on aLED board supporting LED load 10 whereby the temperature-coefficientresistor is in thermal communication with LED load 10.

Sensor 50 is an electronic module structurally configured to sense theflow of LED current I_(LED) through LED load 10, and to generate acurrent-sensing signal CSS that is indicative of the flow of the LEDcurrent I_(LED) through LED load 10 as sensed by sensor 40. Sensor 50 isin electrical communication with current controller 60 to communicatecurrent-sensing signal CSS to current controller 60.

The manner in which sensor 50 senses the flow of LED current I_(LED)through LED load 10, and generates current-sensing signal CSS is withoutlimit. In one embodiment, sensor 50 is in electrical communication withLED load 10 to pull a sensing current I_(SS) from LED load 10 asillustrated in FIG. 1 whereby sensor 50 generates current sensing signalCSS based on sensing current I_(SS).

Current controller 60 is an electronic module structurally configured togenerate temperature-dependent feedback signal TDFS as a function of theoperating temperature of the LED load 10 as indicated bytemperature-sensing signal TSS and the flow of the LED current I_(LED)through LED load 10 as indicated by current-sensing signal CSS. Currentcontroller 60 is in electrical communication with LED driver 30 wherebyLED driver 30 regulates the flow of the LED current I_(LED) through LEDload 10 as previously described herein.

The manner in which current controller 60 generatestemperature-dependent feedback signal TDFS is without limit. In oneembodiment, current controller 60 mixes the temperature sensing signalTSS and the current sensing signal CSS to yield thetemperature-dependent feedback signal TDFS.

Current controller 60 is also structurally configured to generate anopen condition fault signal OCFS whenever current sensing signal CSSindicates LED load 10 is operating as an open circuit Current controller60 is in electrical communication with fault detector 70 to communicateopen condition fault signal OCFS to fault detector 70 upon a generationof open condition fault signal OCFS by current controller 60.

The manner in which current controller 60 generates open condition faultsignal OCFS is without limit. In one embodiment, current controller 60generates open condition fault signal OCFS in response to currentsensing signal CSS being below an open condition fault threshold.

Fault detector 70 is an electronic module structurally configured togenerate a fault detection signal FDS as an indication of a generationof short circuit condition signal SCFS by LED driver 30 or a generationof open condition fault signal OCFS by current controller 60. Faultdetector 70 is in electrical communication with driver disable notifier80 to communicate fault detection signal FDS to driver disable notifier80 upon a generation of fault detection signal FDS by fault detector 70.

The manner in which fault detector 70 generates fault detection signalFDS is without limit. In one embodiment, fault detector 70 employs oneor more electronic switches that transition from a first state (e.g., an“OPEN” switch state) to a second state (e.g., “CLOSED” switch state) inresponse to either short circuit condition signal SCFS or open circuitcondition signal OCFS being communicated to fault detector 70 by LEDdriver 30 or current controller 60, respectively.

Driver disable notifier 80 is an electronic module structurallyconfigured to draw a fault detection current I_(FD) from LED driver 30in response to a generation of fault detection signal FDS by faultdetector 70, and to generate a disable notification signal DNS upon anamperage of fault detection current I_(FD) exceeding a fault detectionthreshold. Driver disable notifier 80 is in electrical communicationwith LED driver disabler 90 to communicate disable notification signalDNS to LED driver disabler 90 upon a generation of disable notificationsignal DNS by driver disable notifier 80.

The manner in which driver disable notifier 80 generates disablenotification signal DNS is without limit. In one embodiment, driverdisable notifier 80 employs one or more electronic switches thattransition from a first state (e.g., an “OPEN” switch state) to a secondstate (e.g., “CLOSED” switch state) to pull fault detection currentI_(FD) from LED driver 30 in response to fault detection signal FDSbeing communicated to driver disable notifier 80 by fault detector 70.This embodiment further employs a fuse component (e.g., a fusistor)whereby fault detection current I_(FD) will blow open the fusistor togenerate the disable notification signal DNS.

LED driver disabler 90 is an electronic module structurally configuredto generate a LED-driver disable signal LDDS as an indication of ageneration of disable notification signal DNS by driver disable notifier80. LED driver disabler 90 is in electrical communication with LEDdriver 30 to communicate LED driver disable signal LDDS to LED driver 30upon a generation of LED driver disable signal LDDS by LED driverdisabler 90.

The manner in which LED driver disabler 90 generates LED driver disablesignal LDDS is without limit. In one embodiment, LED driver disabler 90employs one or more electronic switches that transition from a firststate (e.g., an “OPEN” switch state) to a second state (e.g., “CLOSED”switch state) to generate LED driver disable signal LDDS in response todisable notification signal DNS being communicated to LED driverdisabler 90 by driver disable notifier 80.

An “ON” state operation and an “OFF” stage operation of system 20 willnow be described herein.

An “ON” state operation of system 20 involves an application of “ON”state input voltage V_(ON) to LED driver 30 whereby LED driver 30regulates the flow of LED current I_(LED) through LED load 10 to therebydrive LED load 10 to emit a light. This current regulation by LED driver30 will vary between an upper limit and a lower limit for LED currentI_(LED) based on the sensed operating temperature of LED load 10 and thesensed flow of LED current I_(LED) through LED load 10. This currentregulation by LED load 10 will be continuous until such time (1) the“OFF” state input voltage V_(OFF) is applied to LED driver 30, (2) theLED load 10 operates as an open circuit, or (3) the LED load 10 operatesas a short circuit, which, as previously described herein, encompasses alow LED voltage condition whereby the voltage level of LED voltageV_(LED) is insufficient for driving LED load 10 in emitting a lightduring an application of the “ON” state input voltage V_(ON) to LEDdriver 30. In one embodiment, if a fault condition is detected duringthe “ON” state operation, then fault detection current I_(FS) flowsthrough a fuse component of driver disable notifier 80 until the fusecomponent blows open to thereby disable LED driver 30.

An “OFF” state operation of system 20 involves an application of aninput voltage (not shown) via a high impedance network (not shown)(e.g., 20 KΩ). A conventional conflict monitor (not shown) is utilizedto measure a voltage across input terminals of LED driver 30. In oneembodiment, if a fuse component of driver disable notifier 80 had blownopen during the “ON” state operation as an indication of a faultcondition of system 20, then the voltage measured across the inputterminals of LED driver 30 will exceed a conflict monitor voltagethreshold for facilitating a detection of the fault condition by theconflict monitor. Conversely, if the fuse component of driver disablenotifier 80 had not blow open during the “ON” state operation, then thevoltage measured across the input terminals of LED driver 30 will beless than the conflict monitor voltage threshold whereby the conflictmonitor detects a no-fault operation status of system 20.

In practice, structural configurations of LED driver 30, sensor 40,sensor 50, temperature-dependent current controller 60, fault detector70, driver disable notifier 80 and LED driver disabler 90 are dependentupon a particular commercial implementation of system 20.

FIG. 2 illustrates one embodiment of system 20 (FIG. 1) as a system 200that employs LED driver 300, sensor 400, sensor 500, atemperature-dependent current controller 600, a fault detector 700, adriver disable notifier 800 and a LED driver disabler 900.

LED driver 300 employs an illustrated structural configuration of aconventional electromagnetic filter (“EMI”) 301, a conventional powerconverter (“AC/DC”) 302, capacitors C1-C5, windings PW1-PW3 and SW1 of atransformer, diodes D1-D3, a zener diode Z1, resistors R1-R4, anelectronic switch in the form of a N-Channel MOSFET Q1, an electronicswitch in the form of a NPN bipolar transistor Q2, and a conventionalpower factor correction integrated circuit (“PFC IC”) 303 (e.g., modelL.6561 manufactured by ST Microelectronics, Inc.).

Circuit 303 has a gate driver output GD electrically connected to a gateof MOSFET Q1 to control an operation of MOSFET Q1 as a switch. Resetcoil PW2 is electrically connected to a reset input ZCD of circuit 303to conventionally provide a reset signal (not shown) to circuit 303. Anemitter terminal of transistor Q2 is electrically connected via diode D3to power input V_(CC) of circuit 303 to conventionally provide a powersignal (not shown) to circuit 303. Capacitor C5 is electricallyconnected between a feedback input V_(FB) and a compensation input C+ ofcircuit 303 to facilitate an application to feedback input V_(FB) oftemperature-dependent feedback signal TDFS (FIG. 1) in the form of atemperature-dependent feedback voltage V_(TDFS).

Sensor 400 employs an illustrated structural configuration of resistorsR5-R9, a zener diode Z2, and a negative temperature coefficient resistorR_(NTC) A thermal communication between resistor R_(NTC) and a LED load100 facilitates a generation of temperature sensing signal TSS (FIG. 1)in the form of a temperature sensing voltage V_(TS). In one embodiment,resistor R_(NTC) is formed on a LED board supporting LED load 100 tothereby establish the thermal communication between resistor R_(NTC) andLED load 100.

The illustrated structural configuration of sensor 400 enables aselection of one of many LED operational relationships between theresistive value of resistor R_(NTC) and the flow of LED current I_(LED)through LED load 100. FIG. 3 illustrates a pair of exemplary curvesdepicting the operational relationships between the resistive value ofresistor R_(NTC) and the flow of LED current I_(LED) through LED load100. The first curve is shown as having an upper limit UL1 and a lowerlimit LL1. The second curve is shown as having an upper limit UL2 and alower limit LL2. Those having ordinary skill in the art will appreciatethe required light output of LED load 100 determines the desiredoperational relationship between the resistive value of resistor R_(NTC)and the flow of LED current I_(LED) through LED load 100.

Sensor 500 conventionally employs a sense resistor R10 to facilitate ageneration of current sensing signal CSS (FIG. 1) in the form of currentsense voltage V_(CS).

Current controller 600 employs an operational amplifier U1, anoperational amplifier U2, resistors R11-R14, and a diode D4. Anon-inverting input of operational amplifier U1 is electricallyconnected to sensor 400 whereby temperature-sensing voltage V_(TS) isapplied to the non-inverting input of operational amplifier U1. Anon-inverting input of operational amplifier U2 is electricallyconnected to sensor 500 whereby current sensing voltage V_(CS) isapplied to the non-inverting input of operational amplifier U2.Temperature-dependent feedback voltage V_(TDF) is generated as a mixtureof a temperature feedback voltage V_(TF) generated by operationalamplifier U1 and a current feedback voltage V_(CF) generated byoperational amplifier U2.

In one embodiment, an internal reference signal of circuit 303 is 2.5volts and the illustrated structural configuration of current controller600 is designed to force temperature-dependent feedback voltage V_(TDF)to be 2.5 volts. In design, at the lower end of the operatingtemperature range of LED load 100 operational amplifier U1 is designedto generate temperature sensing voltage V_(TS) approximating 2.5 voltsand a design of an output of operational amplifier U2 in generatingcurrent sensing voltage V_(CS) is adjusted to achieve a lower LEDcurrent limit, such as, for example, lower limits LL1 and LL2illustrated in FIG. 3. In operation, the generation of temperaturesensing voltage V_(TS) and current sensing voltage V_(CS) is inaccordance with the mathematical relationship [1]:(V _(CF)−2.5 volts)/R12=(2.5 volts−V _(TF))/R11  [1]

where a minimum level of temperature sensing signal V_(TS) achieves asuitable upper LED current limit, such as, for example upper limits UL1and UL2 illustrated in FIG. 3.

Fault detector 700 employs an illustrated structural configuration ofresistors R15-R21, capacitors C7-C10, a diode D6, a pair of zener diodeZ3 and Z4, an electronic switch in the form of a PNP bipolar transistorQ3, and an electronic switch in the form of a NPN bipolar transistor Q4.

Resistor R20 is electrically connected to the output of operationalamplifier U2 to establish the electric communication between currentcontroller 600 and fault detector 700. Current sensing voltage V_(CS) isbelow the open condition fault threshold OCFT (e.g., 0 volts) wheneverLED load 100 is operating as a short circuit. As such, current sensingvoltage V_(CF) constitutes open condition fault signal OCFS (FIG. 1)whenever current sensing voltage V_(CF) below the open condition faultthreshold.

Zener diode Z3 is electrically connected to an output of LED driver 300via a diode D5 and a capacitor C6 to establish an electricalcommunication between LED driver 300 and fault detector 700. LED voltageV_(LED) constitutes the short circuit fault signal SCFS (FIG. 1)whenever LED voltage V_(LED) is below the short condition faultthreshold SCFT (e.g., 4 volts), such as, for example, whenever LED loadis operating as a short circuit.

Driver disable notifier 800 employs an illustrated structuralconfiguration of fusistor F1, resistors R22 and R23, zener diode Z5, andan electronic switch in the form of a N-Channel MOSFET Q5. Fusistor F1is electrically connected to LED driver 300 to thereby establish anelectrical communication between LED driver 300 and driver disablenotifier 800. A gate terminal of MOSFET Q5 is electrically connected tofault detector 700 to establish an electrical communication betweenfault detector 700 and driver disable notifier 800.

A fault detection current I_(FD) flows from LED driver 300 throughfusistor F1 whenever MOSFET Q5 is ON. Fusistor F1 is designed to blowwhenever the flow of fault detection current I_(FD) reaches a specifiedamperage level. Disable notification signal DNS (FIG. 1) in the form ofa disable notification voltage V_(DN) is generated upon a blowing offusistor F1.

LED driver disabler 900 employs the illustrated structural configurationof resistors R24-R26, a capacitor C11, a pair of diodes D7 and D8, andan electronic switch in the form of PNP bipolar transistor Q6. Diode D7is electrically connected to fusistor F1 to thereby establish anelectrical communication between driver disable notifier 800 and LEDdriver disabler 900. An emitter terminal of transistor Q6 and diode D8are electrically connected to a base terminal of transistor Q2, anddiode D8 is further electrically connected to power input V_(CC) ofcircuit 303 to establish an electrical communication between LED driver300 and LED driver disabler 900. Power disable signal PDS (FIG. 1) inthe form of power disable voltage V_(PD) is generated at the baseterminal of transistor Q2 upon a generation of disable notificationvoltage V_(DN) by driver disable notifier 800.

An “ON” state operation of system 200 will now be described herein withreference to FIG. 4.

An “ON” state operation of system 200 involves an application of “ON”state input voltage V_(ON) to EMI filter 301 whereby LED driver 300regulates the flow of LED current I_(LED) through LED load 100 tothereby drive LED load 100 to emit a light. Current feedback voltageV_(CF) being greater than an open condition fault threshold voltageV_(OCFT) is indicative of an absence of LED load 100 operating as anopen circuit. LED voltage V_(LED) being greater than short conditionfault threshold voltage V_(SCTF) is indicative of an absence of LED load100 operating in a low LED voltage condition, in particular as a shortcircuit. As such, MOSFET Q1 and transistor Q2 are turned ON wherebycircuit 303 controls an implementation of a pulse width modulation ofthe gate signal applied to MOSFET Q1.

Current feedback voltage V_(CF) being equal to open condition faultthreshold voltage V_(OCFT) is indicative of a presence of LED load 100operating as an open circuit. In such a case, transistor Q3 is turnedON, which turns transistor Q4 OFF. This ensures MOSFET Q5 is fullyturned ON. As a result, fault detection current I_(FD) will flow throughfusistor F1 until fusistor F1 is blown open. Upon fusistor F1 blowingopen, transistor Q6 is turned ON to thereby turn pull the base terminalof transistor Q2 and capacitor C4 to a low voltage state whereby LEDdriver 300 is disabled and MOSFET Q1 is turned OFF.

LED voltage V_(LED) being less than or equal to short condition faultthreshold voltage V_(SCFT) is indicative of a presence of LED load 100operating in a low LED voltage condition, particularly as a shortcircuit. In this case, transistor Q4 turns OFF to turn MOSFET Q5 fullyON. As a result, fault detection current I_(FD) will flow throughfusistor F1 until fusistor F1 is blown open. Again, upon fusistor F1blowing open, transistor Q6 is turned ON to thereby turn pull the baseterminal of transistor Q2 and capacitor C4 to a low voltage statewhereby LED driver 300 is disabled and MOSFET Q1 is turned OFF.

If a fault condition is detected during the “ON” state operation, thenfusistor F1 is blown and LED driver 30 is disabled. Specifically,fusistor F1 is blown open by keeping MOSFET Q5 turned on whereby faultdetection current I_(FD) increases until fusistor F1 blows open.

An “OFF” state operation of system 200 involves an application of aninput voltage (not shown) via a high impedance network (not shown)(e.g., 20 KΩ). A conventional conflict monitor (not shown) is utilizedto measure a voltage across input terminals of LED driver 300. Iffusistor F1 had blown open during the “ON” state operation as anindication of a fault condition of system 200, then the voltage measuredacross the input terminals of LED driver 300 will exceed a conflictmonitor voltage threshold for facilitating a detection of the faultcondition by the conflict monitor. If fusistor F1 had not blow openduring the “ON” state operation, then the conflict monitor voltagemeasured across the input terminals of LED driver 300 will be less thanthe voltage threshold whereby the conflict monitor detects a no-faultoperation status of system 200.

A LED based lighting system 21 (e.g., a traffic light) as illustrated inFIG. 5 controls a flow of a LED current I_(LED) through a LED load(“LL”) 10 in response to an input voltage in the form of either an “ON”state voltage V_(ON) or an “OFF” stage voltage V_(OFF). To this end,system 20 employs power supply (“PS”) 30, LED load temperature sensor(“LLTS”) 40, LED current sensor (“LCS”) 50, a temperature-dependentcurrent controller (“TDCC”) 60, fault detector (“FD”) 70, and a fusenetwork (“FD”) 100.

LED driver 30, sensor 40, sensor 50, current controller 60 and faultdetector 70 operate as previously described herein in connection withFIG. 1, except fault detector 70 is in electrical communication with LEDdriver 30 to communicate fault detection signal FDS to LED driver 30. Inresponse to fault detection signal FDS, LED driver 30 operates toincrease an amperage level of an input current I_(IN) whereby fusenetwork 100, which is an electronic module structurally configured toinclude one or more fuse components (e.g., a fusistor), blows open todisable LED driver 30.

An “ON” state operation and an “OFF” stage operation of system 21 willnow be described herein.

An “ON” state operation of system 20 involves an application of “ON”state input voltage V_(ON) to LED driver 30 via fuse network 100 wherebyLED driver 30 regulates the flow of LED current I_(LED) through LED load10 to thereby drive LED load 10 to emit a light. This current regulationby LED driver 30 will vary between an upper limit and a lower limit forLED current I_(LED) based on the sensed operating temperature of LEDload 10 and the sensed flow of LED current I_(LED) through LED load 10.This current regulation by LED load 10 will be continuous until suchtime (1) the “OFF” state input voltage V_(OFF) is applied to LED driver30, (2) the LED load 10 operates as an open circuit, or (3) the LED load10 operates as a short circuit, which, as previously described herein,encompasses a low LED voltage condition whereby the voltage level of LEDvoltage V_(LED) is insufficient for driving LED load 10 in emitting alight during an application of the “ON” state input voltage V_(ON) toLED driver 30.

An “OFF” state operation of system 21 involves an application of aninput voltage (not shown) via a high impedance network (not shown)(e.g., 20 KΩ). A conventional conflict monitor (not shown) is utilizedto measure a voltage across input terminals of LED driver 30. In oneembodiment, if fuse network 100 had blown open during the “ON” stateoperation as an indication of a fault condition of system 21, then thevoltage measured across the input terminals of LED driver 30 will exceeda conflict monitor voltage threshold for facilitating a detection of thefault condition by the conflict monitor. Conversely, if the fuse network100 had not blow open during the “ON” state operation, then the voltagemeasured across the input terminals of LED driver 30 will be less thanthe conflict monitor voltage threshold whereby the conflict monitordetects a no-fault operation status of system 21.

Alternatively, the conflict monitor could measure an “ON” state inputline current I_(IN) to detect any fault condition of system 21. In thecase, if fuse network 100 blows open during the “ON” state operation,then the ON” state input line current I_(IN) will be less than aconflict monitor current threshold for facilitating a detection of thefault condition by the conflict monitor. Conversely, if the fuse network100 does not blow open during the “ON” state operation, then the ON”state input line current I_(IN) will be greater than the conflictmonitor current threshold whereby the conflict monitor detects ano-fault operation status of system 21.

In practice, structural configurations of LED driver 30, sensor 40,sensor 50, temperature-dependent current controller 60, fault detector70, and fuse network 100 are dependent upon a particular commercialimplementation of system 20.

FIG. 6 illustrates one embodiment of system 21 (FIG. 5) as a system 201that employs LED driver 300, sensor 400, sensor 500,temperature-dependent current controller 600, fault detector 700, and afuse network 1000. LED driver 300, sensor 400, sensor 500, currentcontroller 600 and fault detector 700 operate as previously described inconnection with FIG. 2. Fuse network 1000 includes a fusistor F2electrically connected in series between an input terminal and EMIfilter 301.

An “ON” state operation of system 201 will now be described herein withreference to FIG. 7.

An “ON” state operation of system 201 involves an application of “ON”state input voltage V_(ON) to EMI filter 301 via fusistor F2 whereby LEDdriver 300 regulates the flow of LED current I_(LED) through LED load100 to thereby drive LED load 100 to emit a light. Current feedbackvoltage V_(CF) being greater than an open condition fault thresholdvoltage V_(OCFT) is indicative of an absence of LED load 100 operatingas an open circuit LED voltage V_(LED) being greater than shortcondition fault threshold voltage V_(SCTF) is indicative of an absenceof LED load 100 operating in a low LED voltage condition, in particularas a short circuit. As such, MOSFET Q1 and transistor Q2 are turned ONwhereby circuit 303 controls an implementation of a pulse widthmodulation of the gate signal applied to MOSFET Q1.

Current feedback voltage V_(CF) being equal to open condition faultthreshold voltage V_(OCFT) is indicative of a presence of LED load 100operating as an open circuit. In such a case, transistor Q3 is turnedON, which turns transistor Q4 OFF. As a result, fault detection voltageV_(FD) is applied to the gate to MOSFET Q1 to thereby pull input currentI_(IN) at amperage level sufficient to blow open fusistor F2.

LED voltage V_(LED) being less than or equal to short condition faultthreshold voltage V_(SCFT) is indicative of a presence of LED load 100operating in a low LED voltage condition, particularly as a shortcircuit. In such a case, transistor Q4 turns OFF to apply faultdetection voltage V_(FD) to the gate terminal of MOSFET Q1 whereby LEDdriver 300 pulls input current I_(IN) at amperage level sufficient toblow open fusistor F2.

An “OFF” state operation of system 201 involves an application of aninput voltage (not shown) via a high impedance network (not shown)(e.g., 20 KΩ). A conventional conflict monitor (not shown) is utilizedto measure a voltage across input terminals of LED driver 300 In oneembodiment, if fusistor F2 had blown open during the “ON” stateoperation as an indication of a fault condition of system 201, then thevoltage measured across the input terminals of LED driver 300 willexceed a conflict monitor voltage threshold for facilitating a detectionof the fault condition by the conflict monitor. Conversely, if fusistorF2 had not blow open during the “ON” state operation, then the voltagemeasured across the input terminals of LED driver 300 will be less thanthe conflict monitor voltage threshold whereby the conflict monitordetects a no-fault operation status of system 201.

Alternatively, the conflict monitor could measure an “ON” state inputline current I_(IN) to detect any fault condition of system 201. In thecase, if fusistor F2 blows open during the “ON” state operation, thenthe ON” state input line current I_(IN) will be less than a conflictmonitor current threshold for facilitating a detection of the faultcondition by the conflict monitor. Conversely, if fusistor F2 does notblow open during the “ON” state operation, then the ON” state input linecurrent I_(IN) will be greater than the conflict monitor currentthreshold whereby the conflict monitor detects a no-fault operationstatus of system 201.

While the embodiments of the invention disclosed herein are presentlyconsidered to be preferred, various changes and modifications can bemade without departing from the spirit and scope of the invention. Thescope of the invention is indicated in the appended claims, and allchanges that come within the meaning and range of equivalents areintended to be embraced therein.

1. A system (20) for supplying power to an LED load (10), the system(20) comprising: a LED driver module (30) operable to regulate a flow ofa LED current (I_(LED)) through the LED load (10) as a function of atemperature-dependent feedback signal (TDFS); and a current controllermodule (60) in electric communication with said LED driver module (30)to communicate the temperature-dependent feedback signal (TDFS) to saidLED driver module (10), wherein said current controller module (60) isoperable to generate the temperature-dependent feedback signal (TDFB) asa function of an operating temperature of the LED load (10) and the flowof the LED current (I_(LED)) through the LED load (10).
 2. The system(20) of claim 1, wherein said current controller module (600) includes:means for generating a temperature feedback voltage (V_(TF)) as afunction of a sensed operating temperature of the LED load (10); meansfor generating a current feedback voltage (V_(CF)) as a function of asensed flow of the LED current (ILED) through the LED load (10); andmeans for mixing the temperature feedback voltage (V_(TF)) and thecurrent feedback voltage (V_(CF)) to yield the temperature-dependentfeedback signal (TDFB)
 3. The system (20) of claim 1, wherein saidcurrent controller module (600) includes: an operational amplifier (U1)operable to generate a temperature feedback voltage (V_(TF)) as afunction of the operating temperature of the LED load (10).
 4. Thesystem (20) of claim 3, further comprising: a LED temperature sensormodule (40) operable to sense the operating temperature of the LED load(10) and to generate a temperature sensing signal (TSS) indicative ofthe operating temperature of the LED load (10) as sensed by said LEDtemperature sensor module (40), wherein said LED temperature sensor (40)is in electrical communication with said current controller module (60)to communicate the temperature-sensing signal (TSS) to said operationalamplifier (U1) whereby said operational amplifier (U1) generates thetemperature feedback voltage (V_(TF)) as a function of the operatingtemperature of the LED load (10).
 5. The system (20) of claim 4, whereinsaid temperature sensor module (40) includes: a temperature coefficientresistor (R_(NTC)) in thermal communication with the LED load (10) tothereby sense the operating temperature of the LED load.
 6. The system(20) of claim 1, wherein said current controller module (60) includes:an operational amplifier (U2) operable to generate a current feedbackvoltage (V_(CF)) as a function of the flow of the LED current (I_(LED))through the LED load (10).
 7. The system (20) of claim 6, furthercomprising: a LED current sensor module (50) operable to sense the flowof the LED current (I_(LED)) through the LED load (10) and to generate acurrent sensing signal (CSS) indicative of the flow of the LED current(I_(LED)) through the LED load (10) as sensed by said LED current sensormodule (50), wherein said LED current sensor module (50) is inelectrical communication with said current controller module (60) tocommunicate the current sensing signal (CSS) to said operationalamplifier (U2) whereby said operational amplifier (U2) generates thecurrent feedback voltage (V_(CF)) as a function of the flow of the LEDcurrent (I_(LED)) through the LED load (10).
 8. The system (20) of claim1, further comprising: a fault detector module (70) operable to generatea fault detection signal (FDS) in response to the LED load (10)operating as an open circuit; and a driver disable notifier (80) inelectrical communication with said fault detector module (70) to receivea communication of the fault detection signal (FDS) from said faultdetector module (70), said driver disable notifier (80) including afusistor (F1) operable to blow open in response to a reception of thefault detection signal (FDS) by said driver disable notifier (80). 9.The system (20) of claim 8, further comprising: a LED driver disablermodule (90) operable to disable said LED driver module (30) in responseto a blowing open of said fusistor (F1).
 10. The system (20) of claim 1,further comprising: means for generating a fault detection voltage(V_(FD)) as a function of the LED load (10) operating as an opencircuit; and a driver disable notifier (80) including a fusistor (F1),and means for blowing open said fusistor (F1) in response to ageneration of the fault detection voltage (V_(FD)).
 11. The system (20)of claim 10, further comprising: means for disabling said LED drivermodule (30) in response to a blowing open of said fusistor (F1).
 12. Thesystem (20) of claim 1, further comprising: a fault detector module (70)operable to generate a fault detection signal (FDS) in response to theLED load (10) operating as a short circuit; and a driver disablenotifier (80) in electrical communication with said fault detectormodule (70) to receive a communication the fault detection signal (FDS)by said fault detector module (70), said driver disable notifier (80)including a fusistor (F1) operable to blow open in response to areception of the fault detection signal (FDS) by said driver disablenotifier (80).
 13. The system (20) of claim 12, further comprising: aLED driver disabler module (90) operable to disable said LED drivermodule (30) in response to a blowing open of said fusistor (F1).
 14. Thesystem (20) of claim 1, further comprising: means for generating a faultdetection voltage (V_(FD)) as in response to the LED load (10) operatingas a short open circuit; and a driver disable notifier (80) including afusistor (F1), and means for blowing open in response to a generation ofthe fault detection voltage (V_(FD)).
 15. The system (20) of claim 14,further comprising: means for disabling said LED driver module (30) inresponse to a blowing open of said fusistor (F1).
 16. The system (20) ofclaim 1, further comprising: a fusistor (F2) in electrical communicationwith said LED driver module (30), wherein said fusistor (F2) is operableto blow open in response to the LED load (10) operating as an opencircuit, and wherein said LED driver module (30) is disabled in responseto a blowing open of said fusistor (F2).
 17. The system (20) of claim 1,further comprising: a fusistor (F2) in electrical communication withsaid LED driver module (30), wherein said fusistor (F2) is operable toblow open in response to the LED load (10) operating as a short circuit,and wherein said LED driver module (30) is disabled in response to ablowing open of said fusistor (F2).
 18. A method for supplying power toan LED load (10), the method comprising: generating a current-sensingsignal (CSS) indicative of a flow of a LED current (I_(LED)) through theLED load (10); generating a temperature-sensing signal (TSS) indicativeof an operational temperature of the LED load (10); and regulating theflow of the LED current (I_(LED)) through the LED load (10) as afunction a mixture of the current-sensing signal (CSS) and thetemperature-sensing signal (TSS).
 19. The method of claim 18, furthercomprising: monitoring the operating condition of the LED load (10); andceasing the flow of the LED current (I_(LED)) through the LED load (10)in response to the LED load (10) operating as one of an open circuit ora short circuit.
 20. The method of claim 19, further comprising: blowingopen a fusistor (F1, F2) in response to the LED load (10) operating asone of an open circuit or a short circuit; and ceasing the flow of theLED current (I_(LED)) through the LED load (10) in response to thefusistor (F1, F2) being blow open.